Pneumatic springs commonly referred to as air springs, have been used with motor vehicles for a number of years to provide cushioning between movable parts of the vehicle, primarily to absorb shock loads impress on the vehicle axles by the wheels striking an object in the road or falling into a depression. These air springs usually consist of a flexible elastomeric sleeve or bellows containing a supply of compressed air or other fluid and having one or more pistons located within the flexible sleeve to cause compression and expansion as the vehicle experiences the road shocks. The pistons cause compression and expansion within the spring sleeve and since the sleeve is of a flexible material permits the pistons to move axially with respect to each other within the interior of the sleeve. The ends of the sleeve usually are sealingly connected to the pistons or end members and have one or more rolled ends which permit the end members to move axially with respect to each other between a jounce or collapsed position and a rebound or extended position without damaging the flexible sleeve.
It is desirable that a damping mechanism or device be used in combination with such air springs to provide damping for controlling the movement of the air springs. One type of vehicle damping is achieved through a separate oil filled device providing a hydraulic type of damping by restricting the flow of oil through a series of orifices. Other air springs use a fluid shock absorber strut in combination with the air spring to provide the desired damping. Still other devices use an external reservoir and solenoid control valve for regulating the fluid pressure in the interior of the air spring sleeve or bellows.
It is desirable to provide an air spring having an inexpensive, efficient, and relatively maintenance free device which will supply internal damping to an air spring comparable to that provided by a hydraulic shock absorber thereby eliminating the need of an external shock absorber, which will have very little effect on the lateral, vertical and torsional performance of the air spring sleeve, and which can be positioned to provide a desired amount of damping in either the jounce or rebound direction.
U.S. Pat. No. 3,831,628 discloses a check valve comprising a flat ring and a flexible one-way valve used to control fluid flow between pipes. The valve opens when a predetermined fluid flow rightfully occurs.
U.S. Pat. No. 3,883,030 discloses a breather cap for a brake which includes a unidirectional valve. The breather valve is lifted off its seat to permit air to flow freely into the atmosphere. When the valve is closed, that is when the interior pressure becomes less than atmospheric, it rests on its seat which has roughened portions which prevent a perfect seal and permits air to flow around the valve.
U.S. Pat. No. 3,901,272 discloses a unidirectional flow valve having an openable central slit which controls fluid flow through the valve. Higher pressure in one passageway maintains the slit closed around a wire to permit only a controlled air flow into another passageway. Higher internal pressure causes the flaps to move and permits free air to flow between the two passageways.
U.S. Pat. No. 4,383,679 discloses a damper device for suspension of an engine. The device includes armatures and an elastic block interposed between them. A plate divides a bore into two chambers and has an orifice tube which provides an unrestricted flow communicating between the two chambers.
Russian Pat. No. 783,515 discloses a pneumatic spring damper having bellows-type rubberized cord casing, a damping chamber and a hemisphere cap set clear of the cover, side and bottom of the cap. Due to the motion of the fibroid objects in the downward direction, air flows from the rubberized cord casing through the opening in the cover and into the bottom of the cap.
Russian Pat. No. 1,100,442 discloses a pneumatic vibration damping element having a bellows-type rubber coated envelope. A belt is pressed against rubber reinforcement and air from the rubber cord envelope flows into a damping chamber through an aperture at a low resistance and through a pipe having a high resistance, and then through nozzles. The vibrations are dampened by interaction of streams flowing from the orifice and nozzle. The higher the traveling speed of the objects to be isolated from the vibrations, the more effective is the interaction of the air streams and the greater the damping resistance.
Therefore, the need exists for a damping device, and in particular for an inexpensive, relatively maintenance free, valve which can be used in combination with an air spring or pneumatic shock absorber strut for controlling the damping of the device.